Studies are being conducted to define the importance of the formation of 2-hydroxylated estrogens (catechol estrogens) by neural tissue in mammals. Two major approaches are being pursued: 1) A study of estrogen-2-hydroxylase in rat brain, its anatomical and subcellular distribution and its regulation by factors known to be involved in the regulation of reproduction function. 2) A use of neural tissues in culture to define the nature of the interactions of catechol estrogens with receptors for catecholamines and with enzymes that regulate the biosynthesis and degradation of catecholamines. These studies should provide basic information on the function and the mechanism of action of catechol estrogens in relation to central regulation of gonadotrophin release, reproductive behavior and mood changes related to ovarian function.